Automatic process line

ABSTRACT

Automatic process line for exposing photosensitive printing plates with a film and a mask, if any, lying thereon, in a light box. Magazines (13, 14, 15) for plate, film and mask are disposed one above the other in said order from top downwards, displaced in stepped relationship to each other at one side thereof with the lowermost magazine projecting furthest. Moreover, means (20) are provided for picking up plate, film and mask separately at said one side and for picking up the plate also at the opposite side and for displacement thereof stepwise from the pick-up position to a deposit position at said one side of the magazines as well as disposition of plate, film and mask in registered position one on top of the other. A transfer member (33) is provided for receiving plate, film and mask in the deposit position and transferring them to a light box (42) with plate, film and mask in exposure position.

The invention relates to an automatic process line for exposingphotosensitive printing plates with a film and a mask, if any, lyingthereon, in a light box.

Accordingly, the present case concerns an apparatus for handling suchaluminium plates having a photosensitive layer, which are used foroffset printing and which are bent, after exposure and development, attwo opposite edges then to be mounted on a printing cylinder in theprinting press. The processing of the plates in case of multi-colourprinting with text as well as pictures is very heavy and complicatedbecause it may be necessary to expose a single plate several times incombination with different films and masks before the plate isdeveloped, and this gathering of plates, films and masks is not onlytime consuming but also necessitates great care and precision in orderthat each plate will be properly exposed. Automatically functioningapparatus for manufacturing plates is known which is used for printingof black and white only but, as far as is known, not for manufacturingplates for multi-colour printing although there exists a clear demand ofthe possibility of preparing such plates of high quality rapidly and bysmall manual efforts.

The object of the invention is to satisfy this demand and to provide anapparatus which is well suited for automation by application of commoncontrol technique such that the preparation of the plates can follow apredetermined program without manual intervention.

According to the invention said object is achieved by providing anautomatic process line of the kind referred to herein having thecharacteristics appearing from claim 1.

In order to explain the invention in more detail reference is made tothe accompanying drawings in which

FIG. 1 is a side view of the automatic process line of the invention inone embodiment thereof,

FIG. 2 is an enlarged view of a portion of FIG. 1 and

FIG. 3 is a fragmentary sectional view along line III--III in FIG. 2,

FIG. 4 is an enlarged side view of a frame With suction nozzles formingpart of the process line, in a position above a cassette shown insectional view,

FIG. 5 is a diagrammatic and fragmentary side view of control means forcentering plate, film and mask on a light box when the plate is beingexposed,

FIG. 6 is a front view of a glass pane on the light box.

FIG. 7 is a diagrammatic and fragmentary side view of the light box andthe sealing door thereof,

FIG. 8 is a plan view of a code templet for automatically controllingthe processing of plates, films and masks,

FIG. 9 is a plan view of a coded film disposed on the code templet, and

FIG. 10 is a vertical sectional view of means for reading the code.

In FIG. 1 the process line is shown in its entirety. It is built up on aframework 10 including an inclined magazine section 11 shown in enlargedview in FIGS. 2 and 3. In the magazine section guides 12 are providedfor the insertion of three cassettes 13, 14 and 15, the cassette 13being intended for a stack of masks, the cassette 14 for a stack offilms, and the cassette 15 for a stack of aluminium plates having aphotosensitive layer. On each cassette the stacks supported thereonshould be located in a predetermined position by means of guide pinspenetrating through register apertures in the plates, films and masks.The Cassettes are arranged in parallel with each other and are mutuallyspaced but are not one exactly below the other; they are displacedlaterally such that the lowermost cassette with the masks is locatedfurthest to the right, the other cassettes being displaced inwardly instepped relationship so that a portion of the lowermost cassette and theintermediate cassette is freely available from above at the right-handedge. The three cassettes can be duplicated such that two cassettes aredisposed one beside the other at each level perpendicularly to the planeof the drawing as will be seen from FIG. 3 as far as the cassettes 15for the plates are concerned.

In the magazine section 11 of the framework 10 a carriage 20 isdisplaceably guided by connection to a linearly operating ball screw 21for displacement of the carriage between an end position to the left inFIGS. 1 and 2 as shown in these figures, and an end position to theright. The carriage has means for picking up plates, films and masks oneat the time from the related cassettes. For picking up the plates fromthe cassettes 15 there is provided for each cassette a frame 22 guidedfor movement on the carriage perpendicularly to the path of movement ofthe carriage by means of a projecting bar 23 running between groovedpulleys 24. A pneumatic ram 25 is engaged between the carriage and eachframe to provide vertical movement up and down of the frame The framecarries two suction cups 26 and a third suction cup 27 said lattersuction cup being of the bellow type, cf. FIG. 4, to grip the uppermostplate of the stack in the cassette 15 at the right- and left-hand edgesas seen in FIGS. 1 and 2. A nozzle 28 is provided to blow an air jetunder the suction cup 27 as will also be seen from FIG. 4. Suction cups29 and 30, respectively, in combination with a suction cup of the bellowtype and a nozzle are guided in a corresponding manner on the carriagefor movement up and down such movement being provided by means of 6pneumatic rams 31 and 32, respectively, for picking up the films and themasks, respectively, one at the time from the related cassettes but atthe right-hand edge only as seen in FIGS. 1 and 2. When vacuum isapplied in the suction cups the suction cup of bellow type will lift thecorner of the related plate, film or mask an air jet at the same timebeing blown from the nozzle under the raised corner to separate theraised element from the rest of elements received by the relatedcassette. Films and masks are available so as to be gripped at theright-hand edge only, and it is possible to pick up these elements inthe manner described and then to drag them from the cassettes by themovement of the carriage because neither the films nor the masks will bedamaged by such treatment. The plates, however, must be liftedcompletely free when they are picked up because the photosensitive layerotherwise can be damaged because it is easily damaged by mechanicalinfluence. The advantage of the arrangement described is that thecarriage by a single movement to the right from the position shown cancarry plate, film, and mask from the three cassettes arrangedstationarily one above the other, for deposition to the right of thecassettes.

For the reception of plate, film and mask--all at the same time or onlyone or two thereof--at the deposition there is provided a transfer plate33 supported by arms 34 which are mounted for pivotal movement about ahorizontal shaft 35 on the framework and can be swung by means of apneumatic ram 36 engaged between the framework and the arms, from theposition shown by solid lines in FIG. 1, to the position shown by dashlines in FIG. 1. The transfer plate is provided at the edge thereofwhich is located at the top in the position shown by dash lines in FIG.1, with a number of mechanical grippers 37 connected to a pneumaticoperating ram 38.

It is assumed that the transfer plate is in the position shown by solidlines, the plate having been swung to this position by means of the ram36. It is also assumed that the carriage 20 by means of the suction cupsthereof has picked up a mask, a film and a plate. The carriage is nowmoved to the right by means of the ball screw 21, the mask and the filmbeing dragged from the related cassettes while the plate is transportedlifted from the associated cassette. The movement of the carriage iseffected stepwise, which can easily be arranged by programmed operationof the ball screw. In a first stop position the mask is centered on thetransfer plate and will be deposited thereon, after a further movementto the right the film is centered on the transfer plate and will bedeposited onto the mask, and after a further movement to the right theplate is centered on the transfer plate and will be deposited onto thefilm in the right-hand end position of the carriage. Mask, film andplate are all released onto guide pins 39 which correspond to the pinsin the cassettes and are held in a projecting effective position bymeans of a pneumatic ram 40, the pins penetrating into the registerapertures in mask film and plate. The mechanical grippers 37 are thenoperated by means of the ram 38, and when the guide pins 39 have beenwithdrawn, the transfer plate Can be swung by means of the ram 36 to theposition shown by dash lines in FIG. 1, conveying the mask, film andplate which in this position depend vertically affixed by means of thegrippers 37.

In the position shown by dash lines in FIG. 1 the transfer plate is in aposition opposite to an end of a light box 42, said end being covered bymeans of a glass pane 41. At this end the light box can be closed bymeans of a door 43 constructed as a vacuum box. The door can bedisplaced by parallel motion between an open position shown by solidlines in FIG. 1, and a closed position shown by dot-and-dash lines inFIG. 1, by means of a pneumatic ram 44. When the transfer plate 33 hasbeen swung upwards to the position thereof opposite to the light box,plate, film and mask shall be transferred to the vacuum box. For thispurpose guide pins are provided which can be displaced axially by meansof pneumatic rams. The form of the guide pins will be seen from FIG. 5.Each pin has a narrower portion 45A and a thicker portion 45B a conicaltransition being provided therebetween. The size of the registerapertures corresponds to the thicker portion. The pins are projected andare inserted at the narrower portion into the register apertures inplate, film and mask. The grippers 37 can now be disengaged, and thetransfer plate will be swung downwards to the lower position thereof.

The light box is closed by moving the vacuum box towards the glass pane41 of the light box the final exact centration of the plate, film andmask being provided by the thicker portion 45B of the pins penetratinginto the register apertures. At the same time the pins are moved intobores 45C in the light box. Then, the plate can be exposed.

When the exposure has taken place the vacuum box will be returned to theposition shown by solid lines in FIG. 1. In order to selectively graspand release exposed plate, film and mask suction cups and suctionopenings are provided to act on these elements selectively. Referring toFIGS. 6 and 7 there are provided in the vacuum box 43 suction cups 46 toaffix the exposed plate 15A. In the glass pane 41 of the light box 42two suction grooves 47 and 48 are arranged in a rectangle one outsidethe other. Since the film format is larger than the mask format the film14A affixed by means of the outer suction groove 47 can be released withthe mask 13A remaining on the glass pane. Thus, the mask cannot bereleased if the film is not also released but there is no need of doingso.

Means for carrying away plate, film and mask after the exposure areprovided below the light box. Such means comprise a carriage 49 mountedfor pivotal movement in the framework, said carriage being displaceablebetween a receiving position (shown in FIG. 1) and a withdrawn positionby means of a pneumatic ram 50. A carriage is provided with two outputpassages 51 and 52, passage 51 connecting to a box 53 for the receptionof films and masks when they have been finally utilized, and passage 52connecting to a developer 54 when the carriage is in the receivingposition. The carriage 49 is positioned in the receiving position withthe passage 51 located for the reception of film and mask from the glasspane of the light box and with the passage 52 located for the receptionof the plate.

As mentioned above it is necessary to expose in multi-colour printing asingle plate several times, different films and masks being used. Thismeans that the transfer plate 33 with the plate remaining on the vacuumbox in some instants must fetch only a new film or a new film and a newmask. The process line described is well suited for automation byapplication of conventional control technique to selectively pick up andremove plates, films and masks. A simple manner of control comprisesapplication of a code on films and masks, said code being read andsignals produced by the reading being used for initiating the sequencesrequired for performing the exposure according to the prescribed programwhich has been set up by classifying and marking films and masks in asuitable way. FIG. 8 discloses a code templet intended for use as atemplet for code marking of mask and film. The code templet of FIG. 8should be placed as a support on the light table which is used inproducing film and mask, respectively. The templet has a number ofcircular markings 55 corresponding to different instructions to thecontrol system of the process line. The film and the mask, respectively,according to FIG. 9 has a transparent edge portion 56 and is locatedwith this edge portion in a fixed position on the code templet. By meansof a black Indian ink pen opaque markings 57 are made in register withthe relevant circular markings to code the film or mask, respectively.Instead of providing a transparent edge portion or another transparentfield on the film or mask, respectively, circular apertures can bepunched in an opaque portion of the film or mask, respectively,replacing said opaque markings.

FIG. 10 illustrates how the provided coding can be read when the film ormask, respectively, has been lifted to the upper position thereof bymeans of the suction cups before the movement of the carriage 20 isinitiated. Transmitters 58 such as lamps or photo diodes the number ofwhich equals the number of circular markings 55 (14 in number) and whichare distributed in a corresponding row on each frame 22, and acorresponding number of receivers 59 such as photocells arranged in acorresponding way in stationary position on the framework 10 interact toread the code marking on the film or mask, respectively, and forward viaelectronic circuits corresponding signals to the control system of theprocess line, the signal pattern being defined in dependence on specificcode marking positions being inked or perforated, respectively, or not.Plate, film and mask are picked up in the required combinations and arereleased selectively after exposure of the plate in dependence on thecontrol signals obtained.

I claim:
 1. Automatic process line for exposing photosensitive printingplates with a film and a mask, if any, lying thereon, in a light box(42), characterized by magazines (13, 14, 15) for plate, film and maskdisposed one above the other in said order from the top downwards,displaced in stepped relationship to each other at one side thereof withthe lowermost magazine (13) projecting furthest, means (20) for pickingup plate, film and mask separately at said one side and for picking upthe plate also at the opposite side and for displacement thereofstepwise from the pick up position to a deposit position at said oneside of the magazines as well as deposition of plate, film and mask inregistered position one on top of the other, and a transfer member (33)for receiving plate, film and mask in the deposit position andtransferring them to a light box (42) with plate, film and mask inexposure position.
 2. Automatic process line as in claim 1 wherein adoor (43) for closing the light box is constructed as a vacuum box forsupporting the plate, and the light box (42) has vacuum grippers forselected fixation of film and mask.
 3. Automatic process line as inclaim 2 wherein the transfer member (33) can be inserted between thelight box (42) and the vacuum box (43) when the latter box is in theopen position.
 4. Automatic process line as in claim 2 wherein thevacuum box is provided with guide pins for centering plate, film andmask said pins having a narrower portion (45A) to be initially insertedinto plate, film and mask, and a thicker portion (45B) for accuratecentration of plate, film and mask when the vacuum box is closed againstthe light box.
 5. Automatic process line as in claim 1 wherein outputpassages (51, 52) for plate and film and mask, respectively, areadjustably mounted below the light box (42) and the vacuum box (43). 6.Automatic process line as in claim 1 wherein the magazines (13, 14, 15)are mounted in an inclined position and wherein the transfer member (33)comprises a plate mounted for movement in an arc between the depositposition and a position in parallel with the light box (42) over a pivotangle less than 90°.
 7. Automatic process line as in claim 1 to 6wherein film and mask are provided with readable code marking forcontrolling pick up and deposit of plate, film and mask.
 8. Automaticprocess lines as in claim 7 wherein the code marking comprises opaquemarks (57) or perforation in the film or the mask, respectively, andmeans (58, 59) are provided for reading the marks or the perforation,respectively.